If you are using Perl 5.10 or later you can use the smart match operator (~~):

use feature ":5.10"; use strict; use warnings;
my @subset   = qw(a b c e);
my @superset = qw(b a c d x y z);
my $missing = 0;
foreach( @subset ) { $missing++ unless $_ ~~ @superset; }
say "Number missing=$missing";
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